(a) Plans subject to this subchapter. This subchapter applies to all health benefit plans subject to Insurance Code Chapter 1355, Subchapter F, concerning Coverage for Mental Health Conditions and Substance Use Disorders. Health benefit plans subject to Insurance Code Chapter 1355, Subchapter F, are plans that provide benefits or coverage for treatment expenses incurred as a result of a mental health condition or offer mental health or substance use disorder benefits, whether as mandatory coverage under Insurance Code Chapter 1355, concerning Benefits for Certain Mental Disorders, or under another Insurance Code chapter, or as optional coverage (for instance, in an individual short-term limited duration plan).(b) Excepted plans. This subchapter does not apply to a plan that is excepted from:(1) Insurance Code Chapter 1355, Subchapter F, as identified in Insurance Code §1355.253, concerning Exceptions; or(2) Insurance Code Chapter 1425, concerning Application of Subtitle to Certain Coverage, as identified in Insurance Code §1425.001, concerning Exemption from Application of Subtitle.